1. Field of the Invention.
The present invention relates to the field of angioplasty. In particular, the present invention relates to dilatation balloon catheters which are insertable into a patient over a guide wire.
2. Description of the Prior Art.
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating certain types of vascular diseases. In particular, angioplasty is widely used for opening of stenosis in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a balloon catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to reestablish acceptable blood flow through the artery.
Guide wires are often used for establishing the path to the stenoses so that the balloon catheter can subsequently be positioned. The guide wire normally is advanced through the stenosis, and commonly is left in place during the inflation of the balloon.
Balloon catheters used for angioplasty are available in different balloon diameters. There are instances in which it becomes necessary to exchange one size of balloon catheter for another during an angioplasty procedure. When this happens, it is very advantageous to leave the guide wire in place while the first balloon catheter is removed. This allows the second balloon catheter to be reinserted without having to first reestablish the path by inserting a new guide wire.
In the past, however, the removal of the balloon catheter without removing the guide wire has been complicated because the balloon catheter is inserted over the guide wire. To remove the balloon catheter, while leaving the guide wire in place, there must be a portion of the guide wire extending out of the balloon catheter at the proximal end so that the guide wire can be gripped and held in place as the balloon catheter is removed.
One solution is to remove the initial guide wire while leaving the catheter in place and then inserting an "exchange wire" in its place. The exchange wire is long enough so that the portion of its length extending outside of the patient is longer than the length of the catheter. This allows a portion of the exchange wire to be available for gripping at all times regardless of the position of the catheter. There are, however, several problems with this approach. The use of an exchange wire essentially doubles the normal length of the guide wire, which makes the exchange wire difficult to handle and manipulate. This extra length is normally of no use to the physician during angioplasty, since exchanging catheters is required only in a fraction of the total number of angioplasty procedures. The extra steps of exchanging the guide wire for an exchange wire and the increased difficulty of handling a wire of much greater length have been required in the past in order to exchange balloon catheters. A more convenient and easier to use system would be desirable.